Counterbalance apparatus with transverse pneumatic spring and bellcrank linkage

Abstract

A transversely mounted, single pneumatic spring, and dual bell crank and idler link assembly providing a compact counterbalance for hinged closures such as automobile trunk lids. In an automobile trunk installation, the assembly is installed with the spring in lateral disposition in the forward upper portion of the trunk, thus being effectively concealed. Alternative pneumatic spring enhancements, e.g., a multi-output force feature and a pressure decay compensation feature may be incorporated in the spring unit to enhance opening of the lid and to improve life expectancy of the pneumatic spring by minimizing and effectively negating pressure loss due to leakage of gas past the shaft seal. Excess spring cylinder length can provide space or volume zones used for the enhancement features. Structure which provides a multiple output force for the pneumatic spring, utilizes positioning of the spring shaft end bushing and seal to vary the working volume by changing effective cross-section area of the piston shaft near the end of a compression stroke. The extra cylinder length enables a sealed partition wall to separate extra volume and the operative volume part of the cylinder. The extra volume is filled with a supply of gas under higher pressure than that of the spring operative gas pressure and, in conjunction with permeability characterisitcs of the spring shaft seal and the partition wall seal, enables compensation for leakage from the cylinder. Multiple force output provisions can be used in a substantially vertically disposed spring, filled with a predetermined quantity of oil, and used as a liquid-pneumatic shock absorber. A supplemental orifice type disc valve unit can be used in such a shock absorber, located near the closed end of the spring cylinder.

What is claimed and desired to be secured by Letters Patent is: 
     
       1. A counterbalance assembly in combination with a compartment and a compartment closure member, wherein said compartment includes frame structure mounting said counterbalance assembly within said compartment and hingedly mounting said closure member on a hinge axis adjacent said counterbalance assembly: said counterbalance including a single elongate pneumatic spring link comprising a cylinder having one closed end and a reciprocating shaft with one end projecting from the other end of said cylinder, an attachment connector link means on each of the closed cylinder end and the projected end of said shaft, bushing means surrounding said shaft and disposed in and adjacent the other end of said cylinder, and annular seal means within said cylinder, engaging the interior of the cylinder wall, the shaft and said bushing and providing a seal between said shaft and said cylinder wall; said cylinder containing gas under pressure; two bellcranks, each with an intermediate support pivot means and angled arms with each arm carrying a connector means, mounted within said compartment at opposed sides of said compartment, each of the intermediate support pivot means comprise a pivot journal unit rigidly secured on said frame structure; the two bellcranks being disposed in opposed relationship to each other with a first arm of each bellcrank projecting toward and pivotally connected to an associated end connector link means of said pneumatic counterbalance; and elongate connector links, with universal joint connecting means on both ends, each one of said elongate connector links swivelly connected to an associated pivot connector on a second arm of an associated said bellcrank and to said closure member at spaced apart locations on said closure member, a line between said spaced apart locations being offset from the hinge axis of said closure member; whereby closing movement of said closure member to a closed position on said compartment will, via the elongate connector links and associated bellcranks, force said counterbalance shaft to a retracted position in said cylinder; and when the closure member is in said closed position, the output force of said pneumatic counterbalance will, via the bellcranks and elongate connector links, apply a biasing force to the closure member. 
     
     
       2. A counterbalance assembly as defined in claim 1, wherein each of said pivot journal units is an elongate journal stud rigidly secured on said frame structure, each journal stud projecting perpendicular to a plane including the axis of said pneumatic counterbalance. 
     
     
       3. A counterbalance assembly as defined in claim 1, wherein said first bellcrank arms are disposed in a kinematic relationship between the bellcrank intermediate support pivot and its associated connector link means on said pneumatic counterbalance which provides a positive operative angle relative to an aligned dead center relationship between said pneumatic counterbalance and the first bellcrank arms, which kinematic relationship provides that said biasing force by said pneumatic counterbalance when in a retracted position, is toward a closure opening direction. 
     
     
       4. A counterbalance assembly as defined in claim 1, wherein said first bellcrank arms are disposed in a kinematic relationship between the bellcrank intermediate support pivot and its associated connector link means on said pneumatic counterbalance which provides a negative operative angle relative to an aligned dead center relationship between said pneumatic counterbalance and the first bellcrank arms, which kinematic relationship provides that said biasing force by said pneumatic counterbalance, when in a retracted position, is toward a closure closed position. 
     
     
       5. A counterbalance assembly as defined in claim 1, wherein the other end of said cylinder includes means to retain said bushing means within said cylinder against the force of said gas under pressure; a predetermined small quantity of oil being contained in said cylinder; and cooperative means at said other end of said cylinder, including said bushing means, said annular seal means and means external of said cylinder, and adjacent the projected end of said shaft, adapted to engage and reciprocate said bushing means and to thereby reciprocate said annular seal means relative to said cylinder, provide at least a dual output force for said spring link. 
     
     
       6. A counterbalance assembly as defined in claim 5 wherein said cooperative means which provides at least a dual output force for said spring link includes said bushing means and annular seal means which can be axially shifted in said cylinder from and toward said means which retain the bushing means in said cylinder, and the means adjacent said projected end of said shaft comprises first abutment means adapted to engage and force said bushing means further into said cylinder as the retraction movement of said shaft is deliberately forced beyond an intermediate retraction limit position. 
     
     
       7. A counterbalance assembly as defined in claim 6, wherein said shaft has a sufficiently smaller diameter than the other end of said cylinder and its means retaining said bushing means to provide an annular space between said shaft and said cylinder other end; said bushing means includes second abutment means adjacent said other end of said cylinder accessible through said annular space; and said first abutment mean adjacent said projected shaft end comprises means with at least one annular shoulder dimensioned to move into abutment with said second abutment means upon said shaft reaching its said intermediate retraction limit position resulting in an intitial stepped increase in the spring link output force caused by the force due to pressure of the gas within the cylinder acting on the bushing means and its annular seal means being transferred from the cylinder retaining means to an output force on said first abutment means, and upon further retraction movement of said shaft forcing said bushing means and said annular seal means into said cylinder and thereby reducing the working, gas containing, volume of said pneumatic counterbalance, causing an increases in the subsequent slope of the output force relative to axial shaft movement. 
     
     
       8. A counterbalance assembly as defined in claim 7, wherein said bushing includes at least two coaxial cylindrical telescoped parts providing said bushing means, and said annular seal means also includes a annular seal arrangement between said telescoped bushing parts; each bushing part includes end abutment means which comprise said second abutment means; and annular, coaxial abutment shoulder portions adapted to sequentially abut said telescoped bushing parts are provided by said first abutment means adjacent said shaft, whereby progressive further retraction movement of said shaft past its said intermediate retracted position results in a successive sequential abutment with the abutment means of said bushing means parts of sequentially move and then progressively increase the number of said bushing means parts being moved into said cylinder to provide said spring link with at least a triple output force. 
     
     
       9. A counterbalance assembly as defined in claim 1, wherein the other end of said cylinder includes means to retain said bushing means within said cylinder; a predetermined small quantity of oil being contained in said cylinder; said gas in said cylinder is a predetermined accurate quantity of gas under at least several atmospheres of pressure; and wall means are included within said cylinder, at a location between the retracted position of said piston means and said closed cylinder end, fixed at least against movement in a direction toward the other end of said cylinder providing a partition wall dividing said cylinder into plural chambers, the chamber closest to said closed end comprising a fixed volume chamber; said wall means having a peripheral seal means engaging the inner surface of said cylinder and providing a seal against gas flow at least from said fixed volume chamber past the sealing engagement of said peripheral seal means into the remaining space of said cylinder; said fixed volume chamber containing a predetermined quantity of gas under greater pressure than the gas in the remaining space of said cylinder when the shaft is in a retracted condition; said annular shaft seal means and said peripheral seal means having specific gas permeability characteristics, whereby said wall means and the fixed volume chamber with gas under greater pressure provides a pressure decay compensation means aiding maintenance of desired pressure in the cylinder space occupied by said piston shaft. 
     
     
       10. A counterbalance assembly as defined in claim 9, wherein said annular shaft seal means and said peripheral seal means have similar gas permeability characteristics. 
     
     
       11. A counterbalance assembly as defined in claim 9, wherein said annular shaft seal means and said peripheral seal means have different gas permeability characteristics. 
     
     
       12. A counterbalance assembly as defined in claim 9, wherein the other end of said cylinder includes means to retain said bushing means within said cylinder; a predetermined small quantity of oil is contained in said cylinder; and cooperative means at said other end of said cylinder, including said bushing means, said annular seal means and means adjacent said projected end of said shaft, provide at least a dual output force for said spring link. 
     
     
       13. A counterbalance assembly as defined in claim 12, wherein said cooperative means which provides at least a dual output force for said spring link includes bushing means and annular seal means which can be axially shifted in said cylinder from and toward said means which retain the bushing means in said cylinder, and the means adjacent said projected end of said shaft comprises first abutment means adatped to engage and force said bushing means further into said cylinder as the retraction movement of said shaft is deliberately forced beyond an intermediate retraction limit position. 
     
     
       14. A counterbalance assembly as defined in claim 13, wherein said shaft has a sufficiently smaller diameter than the other end of said cylinder and its means retaining said bushing means to provide an annular space between said shaft and said cylinder other end; said bushing means includes second abutment means adjacent said other end of said cylinder accessible through said annular space; and said first abutment mean adjacent said projected end of said shaft comprises means with at least one annular shoulder dimensioned to move into abutment with said second abutment means upon said shaft reaching its intermediate retraction limit position resulting in an initial stepped increase in the spring link output force caused by the force due to pressure of the gas within the cylinder acting on the bushing means and its annular seal means being transferred from the cylinder retaining means to an output force on said first abutment means, upon further retraction movement of said shaft forcing said bushing means and said annular seal means into said cylinder and thereby reducing the working, gas containing, volume of said pneumatic counterbalance, causing an increase in the subsequent slope of the output force relative to axial shaft movement. 
     
     
       15. A counterbalance assembly as defined in claim 14, wherein said bushing includes at least two coaxial cylindrical telescoped parts providing said bushing means, and said annular seal means also includes a annular seal arrangement between said telescoped bushing parts; each bushing part includes end abutment means which comprise said second abutment means; and annular, coaxial abutment shoulder portions adapted to sequentially abut said telescoped bushing parts, are provided by said first abutment means adjacent said shaft, whereby progressive further retraction movement of said shaft past its said intermediate retracted position results in a successive sequential abutment with the abutment means of said bushing means parts to sequentially move and then progressively increase the number of said bushing means parts being moved into said cylinder to provide said spring link with at least a triple output force. 
     
     
       16. A counterbalance assembly as defined in any one of claims 1-14 or 15, wherein said compartment is the trunk of an automobile, said closure member is a trunk lid and said frame structure comprises a part of said trunk located adjacent and spaced from said hinge axis, and a line between said spaced apart locations of the connections of said elongate connector links to said closure member, which is offset from the hinge axis of the closure member, is also parallel to said hinge axis. 
     
     
       17. A pneumatic spring link comprising: a cylinder with a closed end; a piston assembly in said cylinder having a piston shaft with one end projecting from the other end of said cylinder, bushing means on said shaft, an annular seal means around said shaft, a piston means fixed on the other end of said shaft; said other end of the cylinder having means to retain said bushing means within said cylinder; said shaft seal means providing a seal against the cylinder, and a dynamic seal around said shaft; a predetermined quantity of oil being contained in said cylinder; a predetermined accurate quantity of gas under at least several atmospheres of pressure in said cylinder; and cooperative means at said other end of said cylinder, including said bushing means, said annular seal means and means external of the cylinder, and adjacent the projected end of said shaft, providing at least a dual output force for said spring link, wherein said cooperative means which provides the at least dual output force for said spring link includes said bushing means and annular seal means which can be axially shifted in said cylinder from and toward said means which retain the bushing means in said cylinder, and means adjacent said projected end of said shaft comprises first abutment means adapted to engage and force said bushing means further into said cylinder as the retraction movement of said shaft is deliberately forced beyond a normal retraction limit position, wherein said shaft has a sufficiently smaller diameter than the other end of said cylinder and said means retaining said bushing means to provide an annular space between said shaft and said cylinder other end; said bushing means includes second abutment means adjacent said other end of said cylinder accessible through said annular space; and said first abutment mean adjacent said projected end of said shaft comprises means with at least one annular shoulder dimensioned to move into abutment with said second abutment means upon said shaft reaching its intermediate retraction limit position resulting in an initial stepped increase in the spring link output force caused by the force due to pressure of the gas within the cylinder acting on the bushing means and the annular seal means being transferred from the cylinder retaining means to an output force on said first abutment means, upon further retraction movement of said shaft forcing said bushing means and said annular seal means into said cylinder and thereby reducing the working, gas containing, volume of said pneumatic counterbalance, causing an increase in the subsequent slope of the output force relative to axial shaft movement. 
     
     
       18. A pneumatic spring link as defined in claim 17, wherein said at least one annular shoulder has a diametral dimension which enables movement into said cylinder through said annular space upon said further retraction movement of said shaft. 
     
     
       19. A pneumatic spring link as defined in claim 17, wherein said bushing includes at least two coaxial cylindrical telescoped parts providing said bushing means, and said annular seal means also includes a annular seal arrangement between said telescoped bushing parts; each bushing part includes end abutment means which comprise said second abutment means; and annular, coaxial abutment shoulder portions adapted to sequentially abut said telescoped bushing parts are provided by said first abutment means adjacent said shaft, whereby progressive further retraction movement of said shaft past its said intermediate retracted position results in a successive sequential abutment with the abutment means of said bushing means parts to sequentially move and then progressively increase the number of said bushing means parts being moved into said cylinder to provide said spring link with at least a triple output force. 
     
     
       20. A pneumatic spring link as defined in claim 17, 18 or 19, wherein wall means are included within said cylinder, at a location between the fully retracted position of said piston means and said closed cylinder end, fixed at least against movement in a direction toward the other end of said cylinder providing a partition wall dividing said cylinder into plural chambers, the chamber closest to said closed end comprising a fixed volume chamber; said wall means having a peripheral seal means engaging the inner surface of said cylinder and providing a seal against gas flow at least from said fixed volume chamber past the sealing engagement of said peripheral seal means into the remaining space of said cylinder; said fixed volume chamber containing a predetermined quantity of gas under greater pressure than the gas in the remaining space of said cylinder when the shaft is in a retracted condition; said annular shaft seal means and said peripheral seal means having similar gas permeability characteristics, whereby said wall means and the fixed volume chamber with gas under greater pressure provides a pressure decay compensation means aiding maintenance of desired pressure in the cylinder space occupied by said piston shaft.